/agent-tool-contracts

name: agent-tool-contracts
description: "Design agent tools and CLI surfaces—schemas, naming, errors, idempotency, and discoverability for LLM callers. Use when defining tools for agents, SDKs, or AI-native CLIs."
allowed-tools: Read, Glob, Grep

Agent tool contracts

Tool design rules

1. **Verb-noun names** — `search_issues`, `create_draft_pr` (not `doStuff`). 2. **Minimal parameters** — fewer required fields; sensible defaults in description. 3. **Explicit side effects** — "Creates...", "Deletes...", "Read-only" in description. 4. **Bounded output** — paginate or truncate; return summary + pointer for large data. 5. **Stable errors** — `{ "code": "NOT_FOUND", "message": "..." }`.

Schema quality

• Types and enums for categorical fields.
• Examples in parameter descriptions.
• Reject unknown enums at validation layer.

Idempotency and safety

| Operation | Pattern | |-----------|---------| | Read | Safe to retry | | Create | Idempotency key or dedupe by natural key | | Update | Version or ETag when concurrent edits possible | | Delete | Soft delete or two-step confirm in description |

AI-native CLI (when applicable)

• `--json` for machine output; stable field names.
• Exit codes: 0 success, non-zero with stderr message.
• `--dry-run` for mutating commands.

Review checklist

• [ ] Description tells the model when NOT to use the tool
• [ ] Errors actionable (what to fix, not internal codes only)
• [ ] No overlapping tools with ambiguous choice
• [ ] Integration test with representative agent prompts

Related

`mcp-builder` for MCP-specific packaging; `agent-evaluation` for measuring tool accuracy.